Wednesday, May 29

Power Boat Trim for the Beginner

By Andrew Spaulding

The first time I jumped in the family Whaler without parental supervision, I punched the throttle forward just as soon as I left the dock and the bow shot up in the air blocking my vision. This was my first experience with bad trim in a powerboat and it wasn't much fun. Most boats have a way to adjust the trim of the boat through the outboard, sterndrive, or trim tabs. Trimming the boat properly is a way the driver can deliver the safest, smoothest ride for the conditions.

Many beginners drive powerboats around with their bows in the air, because they are unaware how the trim function can change the operation of the boat. This is understandable since there isn't really any equivalent in cars or motorcycles. However, a properly trimmed boat is easier and safer to drive for many reasons.

There are a few key points to trimming a boat properly. Once you understand these and get a little practice, you’ll be driving like a pro in no time. A boat needs to be balanced in two directions – fore-and-aft and side-to-side. A smaller boat without trim tabs needs to move people and stuff side-to-side to get that balance proper. Larger boats with trim tabs can use them to straighten side-to-side trim as well as fore-and-aft. Take care to not use too much trim tab to straighten the boat. Using more trim tab than necessary causes more drag on the boat, slowing the boat and wasting fuel.

Fore-and-aft trim is adjusted on smaller boats with the stern drive angle or outboard angle. Typically, the switch controlling this is on the side of the throttle control. The proper fore-and-aft trim for any size boat will change with the conditions. For popping skiers out or “hole shots”, trim the bow down. This will minimize the cavitation (when the prop breaks loose from the water) and keep the bow down for better visibility.

Generally speaking, as the boat comes up on a plane, you will want to trim up the bow for a smoother ride. If the bow is too low in the water it can catch a wave pushing the boat around making it difficult to steer. However, in rough weather you want to do the opposite. You will want the bow down so that the waves are sliced by the sharp part of the bow, not slamming into the flatter part of the boat bottom behind the bow. In very windy conditions, if the bow is too high, wind can get under the boat causing a dangerous loss of control. When you are pulling a skier or tuber, you should keep the bow trimmed lower. This will help keep the boat from losing speed in sharp turns.

As you are learning to trim a boat properly, make small adjustments to the trim so that you get a feel for how much trim is necessary to make a difference. Since all boats react differently to different trim levels and conditions, practice doing maneuvers at different trim levels while you slowly increase your boat speed and repeat them as necessary to get a feel for the boat. It is easy to get a boat out of control with too much speed and poor trim, so please be careful out on the water.

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